The moves below are for the default table on this site: 6 decks, the dealer stands on soft 17, double after split is allowed, late surrender is allowed and blackjack pays 3 to 2. A few moves change when the rules do; the strategy chart updates for the rules you pick.
The one idea: the dealer's up-card
The dealer has no choices, so their face-up card tells you how likely they are to bust. A 2 to 6 is weak: the dealer is likely to be forced to hit and go over. A 7, 8, 9, 10 or ace is strong: the dealer will often finish with 17 or better. Against a weak card you let the dealer take the risk; against a strong card you have to improve your hand. The dealer bust odds page has the exact numbers for each card.
Hard hands (no ace, or an ace counted as 1)
- 8 or less: always hit.
- 9: double against a 3 to 6, otherwise hit.
- 10: double against a 2 to 9, otherwise hit.
- 11: double against a 2 to 10, hit against an ace.
- 12: stand against a 4, 5 or 6. Hit against everything else, including a 2 or a 3.
- 13 to 16: stand against a 2 to 6, hit against a 7 or higher.
- 17 or more: always stand.
The hands from 12 to 16 are the hard ones, because they lose most of the time whatever you do. The rule of thumb above makes them lose the least. Where surrender is allowed, 16 against a 9, 10 or ace and 15 against a 10 are better surrendered.
Soft hands (an ace counted as 11)
One card cannot bust a soft hand, so you can be bolder. Ace with 2 to 5 (soft 13 to 16) and ace-6 (soft 17) hit, or double against weak dealer cards. Ace-7 (soft 18) is the most-missed hand in blackjack: stand against a 2, 7 or 8, double against a 3 to 6, and hit against a 9, 10 or ace. Ace-8 and ace-9 (soft 19 and 20) always stand.
Pairs
- Aces and 8s: always split.
- 10s: never split.
- 5s: never split; play them as a hard 10 and double.
- 9s: split, except against a 7, 10 or ace, where you stand.
- 7s: split against a 2 to 7.
- 6s: split against a 2 to 6.
- 2s and 3s: split against a 2 to 7.
- 4s: split against a 5 or 6 only; otherwise hit.
Surrender and insurance
Surrender is a small edge that you use rarely. Insurance is the reverse: it pays 2 to 1 on something that happens less than 1 time in 3, so it costs you money. Basic strategy never takes it, and the same goes for "even money" on a blackjack.
How to learn it
Do not try to learn the whole chart in one sitting. Start with the hard totals, then add soft hands, then pairs. Use the strategy quiz, where missed hands come back until you get them. In a coached game the coach tells you whether each move was best and what a different move would cost in chips. For the numbers behind any single hand, put it in the hand calculator.